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MG TD TF 1500 - Shimmy at 55MPH+

We've just installed a new water pump from FTFU and while we had the car on the lift with the radiator out thought we'd see if we could determine why the car (TD25009) shimmies fairly violently at speeds over 55. We couldn't detect anything loose and the wheels appear to run true. I had the wheels lug-centric balanced about a year ago and that does not seem to have helped. The tires are wearing evenly.

The shimmy feels left/right as opposed to up and down which I would expect if it were caused by wheel balance - I'm no expert here so this is just a gut feeling/belief.

What else should I be looking for?

Thanks.

Jud
J K Chapin

A loose tie-rod perhaps?
Jim Rice

You might want to have the brake drums balanced. Some of our club members have done this with surprisingly good results.
gl rombough

It really sounds like a wheel balance issue, maybe try the rear wheels on the front and see if that changes anything
Also 'could' be a dead front shocker, it's the speed where balance issues show up and if there's a dead shocker the wheel just goes out of control

willy
William Revit

JUD,
This is sometimes called the death shimmy... It is usually caused by the WHEELS being out of round or not being "true" ,,, mount them on a balancer and rotate them,, see of you can detect an out of round or not "true" condition

STEVE
SPW Wincze

I have experienced the same thing for years 1954 TF. Have not been able to fix it. New tires, balance all wheels, trued the brake drums. Spent hours on the cement confirming all corners are square. Alignment per the WSM. Some days it's not bad some days it is bad. So I don't drive over 50.
There is a discussion in the archives I think about "Scuttle Shake" or maybe I got that from emails with David Braun.
However, tending to overthink problems, I estimated the natural frequency of the vibration at 12 to 15 Hz.
Which is about the revolution of the tires at 50 MPH.
So, between the tire input and the body sheet metal I feel there is something (wings? Sheet metal? the tube that the scuttle/dash/fire wall?). Something in that mess of parts and panels has a natural frequency that is amplified into this shake and shimmy. On the TF there is a crossbar attaching the two wings together that, I think, is meant to solve this. This leads me to believe the wings are the problem????

Sad news is I've never found a fix for this.
Peter Dahlquist

I also did another thing,, All of our wheels have been on tire changers and balancers many many times,, and they all use cones to mount the wheels using that center hole in the wheel. That center hole has been abused for many years..
I wanted to balance my wheels and tires LUG Centric rather than hole centric,, I stripped out the bearings of a spare brake drum,, and using the bearing surfaces on that drum, had the drum balanced,,,.. Now when I balance new tires, I have the shop mount the spare drum on the balancer,, then mount the wheel and tire to that spare drum,,, now the wheel and tire will rotate as it as it would on the car, not by the old warn out hole in the center of the steel wheel.
It seems to have made a difference!!
SPW Wincze

Thanks Steve and Peter. Yes, I've just worked on a club member's TF and I noted that cross bar on the front wings. I wonder if something similar could be fitted to a TD AND would it make any difference.

The tire shop I use has the attachments for lug centric balancing (I know the center hole is not reliably centered) so I think I have that covered.

The shocks are questionable so while I have the car on my lift I'll at least top up the shock fluid.

As with Peter, I just hold my speed down to 54 on the speedo. That's OK for most of my driving on curvy mountain roads but sometimes a restriction on getting to the start of a drive.

I'll keep plugging at it and if I come up with a magic bullet, I'll let y'all know.

Jud
J K Chapin

While I haven't seen this issue in my cars I have seen it in some I have worked on. I think it's a combination of balance issues but quite often starts with the wheel bearings/hub. I'd raise a wheel and the grasp the tire at 12 o'clock and 6 and try to move the wheel in and out to see if you can feel any aprecciable play. The radial bearings used in our cars have some built in play but some replacements seem to have more and those that have thousands of miles with little to no service will have more. I have also seen hubs where the bearing seat has been wallowed out (I have no idea how) and did not provide a good friction fit. Same for the stub axle. This "looseness" combined with any rotational imbalance acts like an washing machine spinning a heavy load that is bunched up and can be quite violent in action.

If it were my car I would look at balancing the drums as well as converting the front end to tapered bearings.


Just my thoughts
L E D LaVerne

gl rombough and LaVerne -

How do you mount a drum to balance it?

Do you add weights or drill/grind to remove weight?

Need to balance a drum on my TF.

I corrected my out-of-balance front drum by spin balancing on the car. Can’t spin balance rear wheels. Must move to the front to balance. (Not to the side with the out of balance drum!)

https://youtu.be/CFvHeVzhepI

Lonnie
TF681
TF7211
LM Cook

Look up the Mosmatic brake drum balancing machine. Will show how they balance brake drums commercially. You can also check them with a bubble wheel balancer, but the accuracy isn't the greatest. PJ
PJ Jennings

Perhaps when they were told to do a "lug-centric" balance, they took a short cut and did it the easy way? That centric principal also applies to wire wheels. I know of electronic balanced wire wheels shaking hell out of a racing TC .... Cured completely by a static balance.
The article attached is very old but still applies (to bolt-on wheels with accurate centre holes).
Good luck with solving the problem. Let us know what it turns out to be.
Bob


Bob Schapel

To clarify the drums I have seen following “balancing” had evidence of material removal to achieve desired result.
I suspect the “people/shop” that balances you pr clutch etc might be a good place to start.
gl rombough

If you decide to have the wheels balanced on the car -- don't forget to align the adjustment holes in the drums with the holes in the wheels. Bud
Bud Krueger

Hi. JK. As you can see. this cars are not made
with an aerodynamickel front and. there is a lot of
turbulance around the front. How is the steering wheel behaving when the shimming start ?
On my TD4490 there i a bar mounted to the radiatorand the two headlamp brackets on the two wings. The
toe(inout)is imprtent (0).The tire preussure

Thoralf NORWAY TD4490.

.
Thoralf Sorensen (TD4490)

Thoralf, can you post a picture of the "bar mounted to the radiator and the two headlamp brackets on the two wings."?

Yesterday I topped up the front shocks and went for a short drive. The shimmy was not gone but seemed less severe.

Lonnie, I wish we had a shop like that locally. The nearest one that I'm aware of is Hendrix in Greensboro, NC, about 150 miles up the pike. Nonetheless, I'm going to send that neat video to our club members to see if anyone knows of a similar shop around here.

I'm due for new tires pretty soon. My Vredestein SPRINT CLASSICs have performed well and still have good tread after 10 years but that's just about the life of tires so all that good tread will probably be abandoned. That pains my Scottish blood.

Jud

ps: I don't really know if I have any Scottish blood but it makes for a nice phrase.
J K Chapin

Well, I took the TD out for a hard 15 mile run after topping up the front shocks and the shimmy is pretty much gone up to 65 mph on the speedo. I suspect the shocks are leaking so, until they get rebuilt or are replaced, topping them up will be a regular maintenance item.

Jud
J K Chapin

Jud:

What shock/hydraulic fluid did you use? I assume something I can get at a local auto parts store?

Jim
Jim Rice

How is the alignment? Any end play on your steering rack?

Good shocks might be masking your issue.
Regards, Tom
tm peterson

SPW Wincze, Connecticut, USA mentioned it earlier but have you checked the wheels for run out / eccentricity yet ?

I was really surprised at how much mine were out. I ordered 4 second hand ones from well known supplier in the UK who balanced them all before sending. They had them left over from wire wheel conversions. When they arrived they were balanced but not true.

I had at that point I got a local shop who does aluminum wheel repairs to do their best. Nobody in Ireland has the equipment to do it 'properly'. They heated and pressed them. I got four good ones and one acceptable one out of the process.

Made a world of difference to the shimmy... which is gone...

Dave
D Moore

Jim, for shock oil I used is from a bottle labeled "Lever Shock Oil" that I got from the PO when I bought my MGB about 8 years ago. I suspect it was from Moss but I can check tomorrow or Sunday and let you know if that is not the case.

Tom and Dave, I checked the front wheels for run out and they are good to within 1/16 inch. I haven't checked the rears. I wonder if a problem there would manifest itself in what feels like a front end shimmy? I detect no play in the steering rack but I can't say anything about the alignment except that the tires are wearing evenly. Alignment machines that can handle the narrow track of the TD are pretty rare. When I had the MGA aligned it just barely spanned the shop's machine. I think the TD track is narrower than the MGA but my books with those specs are not immediately at hand.

BTW, by "run out" I am assuming that you mean wobble when the wheel turns. I checked this with the car on the lift and a fixed reference point next to the rim. Turning the wheel revealed no change in distance between the rim and the fixed point. Is this what you are referring to?

Thanks.

Jud
J K Chapin

Jim
For shocker oil, if you go to a motorbike workshop/dealer/shop and get some 20weight fork oil, they usually sell it in 1/2 liter (1 pint) bottles
Don't use ordinary hydraulic oil as it doesn't have the anti frothing additives that fork/shocker oil has,
willy
William Revit

Thanks for the tip, Willy -

I’ve been using hydraulic jack oil in the leaking front shocks on TF681. It leaks out so fast that foaming is probably not a problem. I’ll start using a proper shock oil. Rebuild by Peter Caldwell in the future.

Lonnie
TF681
TF7211
LM Cook

Willy/Jud:

Picked up some fork oil yesterday!

Thanks,

Jim
Jim Rice

I solved my scuttle shake at 55+ by having the wheels trued. I had previously tried aligning, balancing and topping the shocks with motorcycle fork oil... all to no avail.

TD wheels are really easily bent, and after so many years of use and abuse they are often really wonky. I had a local rim straightening shop true them up as best he could. I now have 4 decent ones, and a not really great spare.

Scuttle shake is only very barely evident at 55, and the car will go to 70 quite happily.
Kevin McLemore


Jud to your question :"run out" I am assuming that you mean wobble when the wheel turns

Yes :-)

It can be in and out (wheel bent) and hop up and down ( wheel oval).

Sounds like you have tested for this though logically using a fixed reference point against the spinning wheel.

Pick up a dial caliper (for next to no money) at harbor freight and see what that tells you.

Dave

D Moore

Thanks Dave. I have access to a good dial caliper and will recheck the wheels. What kind of tolerances are acceptable? Am I looking for less than 1 mm or is less than 5 or 10 mm OK?

Since I topped up the front shocks the shimmy is much reduced but not gone. I took it out today (35F) for a short drive and had almost no shimmy at 55mph. Perhaps the shock oil was thicker at low temperature. Does shock oil come in different weights (viscosity?) like motor oil? Who knows.

Coming back from our last 150+ mile drive my neighbor's TD started running like crap. At first we thought it might be bad plugs or something in the ignition but all that checked out good so we started on the fuel side. All the filters were clean and the pump was pumping excellently. We decided to check the mixture and balance the carbs. When we went to loosen the connector between the carbs we found that the spring clip (Moss 375-158) had broken so the throttle pedal was opening only one carb. Instead of paying Moss $55 plus shipping, my neighbor fabricated a sleeve bushing with pins through the shafts and his TD is again running great. I'll try to post a picture later. Don't you love cars that can be fixed with chewing gum and baling wire!!

Jud

J K Chapin

Jud, just my opinion, but I believe your shocks are masking your problem. When I got my TD the shocks were empty and just plum worn out. No shimmy.

I eventually had the rebuilt and they are great. My experience (although just a one off) makes me think there is another issue causing the shimmy. You may have reached that conclusion as well.

Regards, Tom
tm peterson

Tom, I'm sort of getting there myself. Jud
J K Chapin

I had pretty much forgotten that I had started this thread. This morning we swapped the front wheels from my neighbor's '51 TD with mine and the shimmy is almost completely gone up to 70+ on the speedo (68mph according to the GPS). With my wheels on Peter's TD he gets the shimmy but not nearly as bad as on mine. I forgot about topping up the shock oil so I'll do that this afternoon. I also forgot to check for wheel bearing play so that's another thing I'll check this afternoon.

We checked the wheel runout with his dial micrometer and it is between 40 and 60 thousandths. I called Hendrix Wheels in Greensboro, NC. Thay cannot true steel wheels but they said that amount of runout is within the "acceptable" range.

Jud

J K Chapin

As a temporary work around try swapping the wheels front to back. Maybe out of round wheels are less of an issue when on the rear?
John Quilter (TD8986)

Thanks. That's Plan B.
J K Chapin

Jud, Have you checked the front end geometry? Easy first step is toe out/toe in. Excessive caster can also cause shimmy.
Regards, Tom
tm peterson

Jud,

I had this problem a few years gao, I changed out the worst wheel with the spare. this made a big difference but didn't totally fix the issue, On further investgating I found that the four bolts that hold the tub to the scuttle hoop to be very loose, I tightened them, would you believe it, problem fixed.

John
J Scragg

I commented above already. There is a lot of hardware on a TD that can excite some vibration. The fender to rad headlight mounts are one. The wings are really heavy and could be prone to go into a natural frequency state at 55 mph or so. On my TF I beefed up the fender to fender stiffener bar.

Another thought the bushings from Moss Motors wear out pretty quick. Can get really sloppy. Went to a stiffer bushing and it help quite a bit.
Peter Dahlquist

john, that's a new one for me but I'll check. Thanks. Jud
J K Chapin

Judd. Just a point on "topping off" shocks. Always leave a small space for air. If you fill it to the top, you put a lot of pressure on the seals and they will leak (or leak even more)

If they leak, the only fix is a rebuild.
Bruce Cunha

This thread was discussed between 31/10/2022 and 05/03/2023

MG TD TF 1500 index

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